The invention relates to the technique of thin layers of platinum oxide deposited on substrates by cathodic spraying or sputtering of a target of platinum in a rarefied oxygen atmosphere.
Such thin layers have great interest in view, on the one hand, of their insulating nature to electricity and their relative transparency and, on the other hand, the very great ease of their transformation, localised or not, into platinum, a metal conducting electricity and opaque to light, such a transformation being obtainable by simple heating to a temperature above 250.degree. C.
In presently known methods of realisation, it has not been possible to produce such thin layers sufficiently pure to be able to draw benefit from the possibility indicated above.
In fact, the electrons which are at the origin of cathodic spraying and which, for this purpose, form a plasma through their impact against the atoms of gas constituting the rarefied atmosphere, are not all consumed by this formation and the platinum oxide molecules developed from platinum atoms extracted from the target by the ions of this plasma are decomposed by the residual electron flow, either in flight, before arriving at the substrate, or after their arrival at this substrate.